Net Maui Platform Windows and Mac Desktop how to access from maui

Question

I have multiple colors of theme on windows and mac How can I access and change colors from maui for setting colors according to theme ? Thanks

<maui:MauiWinUIApplication
    x:Class="XXXDesktop.WinUI.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:maui="using:Microsoft.Maui"
    xmlns:local="using:XXXDesktop.WinUI">
    
    <maui:MauiWinUIApplication.Resources>

        <SolidColorBrush x:Key="ActualWinUITitleBarBrush" Color="#333333" />
        
        
        <StaticResource x:Key="WinUITitleBarBrush" ResourceKey="ActualWinUITitleBarBrush" />
        
        <DataTemplate x:Key="MauiAppTitleBarTemplate">
            <Grid Canvas.ZIndex="1" Height="32" Background="{ThemeResource WinUITitleBarBrush}" VerticalAlignment="Stretch">
                <TextBlock x:Name="AppTitle"  Text="xxx.com"  TextTrimming="CharacterEllipsis" VerticalAlignment="Center" Margin="10,0,0,2"/>
            </Grid>
        </DataTemplate>
    </maui:MauiWinUIApplication.Resources>
</maui:MauiWinUIApplication>

Answer 1

Hello,

You can do this by accessing the SolidColorBrush in the background code, then change the color in the Platforms/Windows/App.xaml.cs. Next, you can invoke this change color code by Messenger - Community Toolkits for .NET | Microsoft Learn.

Firstly, please create a Messager (please install the CommunityToolkit.Mvvm nuget package, before you use it)

// Create a message
public class ChangedThemeColorMessage : ValueChangedMessage<byte[]>
{
     public ChangedThemeColorMessage(byte[] ColorBytes) : base(ColorBytes)
     {
     }
}

Then you can send the message with byte[], byte[] contains color byte. I used button click event for testing.

private void OnCounterClicked(object sender, EventArgs e)
{
    byte[] bytes = { 255, 255, 255, 0 };
     WeakReferenceMessenger.Default.Send(new ChangedThemeColorMessage(bytes));
}

In the end, open your Platforms/Windows/App.xaml.cs and find CreateMauiApp method, you can get the SolidColorBrush by key and change the color from transferred byte[].

protected override MauiApp CreateMauiApp()
{
    WeakReferenceMessenger.Default.Register<ChangedThemeColorMessage>(this, (r, m) =>
    {
        byte[] Colors=  m.Value as byte[];
        if (Colors!=null)
        {
            if (MauiWinUIApplication.Current.Resources.ContainsKey("ActualWinUITitleBarBrush"))
            {
                Microsoft.UI.Xaml.Media.SolidColorBrush brush = MauiWinUIApplication.Current.Resources["ActualWinUITitleBarBrush"] as Microsoft.UI.Xaml.Media.SolidColorBrush;
                if (brush != null)
                {
                    brush.Color = Windows.UI.Color.FromArgb(Colors[0], Colors[1], Colors[2], Colors[3]);
                }
            }


       }   
    });    
    return MauiProgram.CreateMauiApp();
}

Best Regards, Leon Lu

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